There is a mounting concern over future availability of food sources for the world's growing population. The incentive to grow single cell protein from petroleum hydrocarbons is a result of the fact that man is unable to feed himself under the present food distribution system, political climates, and in some locations, the use of poor methods of cultivation and low production of food. Two-thirds of the world's population of about 3.5 billion is reported to be hungry or malnourished. While about 80 million tons of protein are currently produced world-wide each year, the production of protein will have to double merely to keep pace with the world's population by the year 2000, assuming the present rate of growth is maintained.
Many energy sources for microorganisms cannot be used because of their possible inclusion of toxic or carcinogenic material from the substrate into the single cell protein product.
In particular, organic residues containing such toxic elements as copper, zinc, cadmium, tin, lead, arsenic, antimony, selenium, tellurium, nickel, cobalt, chromium, molybdenum, tungsten, vanadium, uranium, thorium and fluorine are avoided as substrates for food producing microorganisms. For example, it is known that cultures that grow on refinery waste effluents assimilate extremely low concentrations of chromium from solution. The fermentation media on which food forming cultures grow should be free of known toxic elements. Coal, for example, cannot be used as a microorganism energy source. Upwards of 40 elements, including several which are toxic, have been identified in coal.
Apart from a lack of aesthetic appeal, cultures grown on substrates containing these or other toxic elements can incorporate small quantities of these elements into the protein and thereby render the product unfit for consumption as a food for higher vertebrates.
Sources of energy in solid form, e.g. plastics and industrial wastes, coals, and coke are for practical purposes unavailable to microorganisms. The growth rate on these solid hydrocarbonaceous sources of energy is too slow to provide a practical way to generate protein. Separation of protein from unreacted solids also poses another obstacle to the use of this type of microorganism substrate. Gasification of these materials and their subsequent conversion into more reactive liquid and/or soluble forms of aliphatic substrates makes their energy content available to the microorganisms.
Microorganism substrate material preferably should be aliphatic compounds such as the linear aliphatic primary alcohols, n-paraffins containing 6 to 20 carbon atoms therein, the fatty acids, aldehydes and linear olefins. Such materials are preferably liquid at fermenter operating temperatures or possess at least limited solubility in the fermenter broth.
It is known to produce a carbon monoxide-hydrogen rich effluent stream from a synthesis gas generator by the partial oxidation of a hydrocarbonaceous fuel.
It is also known that the effluent from the synthesis gas generator can be treated to remove undesirable constituents such as hydrogen and carbon dioxide. Part of the purified effluent comprising carbon monoxide and hydrogen can be used in the synthesis of methanol, and part of the hydrogen employed in the production of ammonia.
It is further known that air can be separated into its major constituents, nitrogen and oxygen, by air rectification.